Base Station, Terminal, and Communication Method

1. A base station comprising: circuitry, which, in operation, selects one of a plurality of cases each indicating a first combination of control channel regions to be monitored by a first terminal among a plurality of control channel regions and a second combination of control channel regions to be monitored by a second terminal among the plurality of control channel regions; and a transmitter, which in operation, indicates, by higher-layer signaling, configuration information indicating the plurality of cases to the first and second terminals, and indicates the selected case by dynamic signaling in the form of a control signal in a DCI (downlink control information) format directed to the first and second terminals, wherein the first combination indicated by the selected case to be monitored by the first terminal is different from the second combination indicated by the selected case to be monitored by the second terminal.

2. The base station according to claim 1 , wherein the transmitter indicates, by the higher-layer signaling, a control channel region for a situation where the dynamic signaling is not received by the first or second terminal, the control channel region being a region to be monitored by the first or second terminal.

3. The base station according to claim 1 , wherein a control channel region to be monitored by the first and second terminals is specified for a situation where the dynamic signaling is not received by the first and second terminals.

4. The base station according to claim 3 , wherein the specified control channel region is at least one of the plurality of control channel regions.

5. The base station according to claim 3 , wherein the specified control channel region is a control channel region having a smallest control channel region number or having a smallest symbol number of a symbol where the control channel region is mapped.

6. The base station according to claim 3 , wherein the specified control channel region is associated with a type of slot in which the dynamic signaling is not received.

7. The base station according to claim 1 , wherein the indicated case for the first terminal is switched among the plurality of cases in accordance with a number of terminals connected to the base station, the terminals including at least the first and second terminals.

8. A first terminal comprising: a receiver, which in operation, receives, from a base station, higher-layer signaling containing configuration information indicating a plurality of cases each indicating a first combination of control channel regions to be monitored by the first terminal among a plurality of control channel regions and a second combination of control channel regions to be monitored by a second terminal among the plurality of control channel regions, and receives, from the base station, dynamic signaling indicating one of the plurality of cases, the dynamic signal being in the form of a control signal in a DCI (downlink control information) format directed to the first and second terminals; and circuitry, which, in operation, detects control information directed to the first terminal in the control channel region corresponding to the one case indicated by the dynamic signaling among the plurality of cases, wherein the first combination indicated by the one case to be monitored by the first terminal is different from the second combination indicated by the one case to be monitored by the second terminal.

9. The first terminal according to claim 8 , wherein the indicated case for the first terminal is switched among the plurality of cases in accordance with a number of terminals connected to the base station, the terminals including at least the first and second terminals.

10. A communication method performed by a base station, the communication method comprising: selecting one of a plurality of cases each indicating a first combination of control channel regions to be monitored by a first terminal among a plurality of control channel regions and a second combination of control channel regions to be monitored by a second terminal among the plurality of control channel regions; and indicating, by higher-layer signaling, configuration information indicating the plurality of cases to the first and second terminals, and indicating the selected case by dynamic signaling in the form of a control signal in a DCI (downlink control information) format directed to the first and second terminals, wherein the first combination indicated by the selected case to be monitored by the first terminal is different from the second combination indicated by the selected case to be monitored by the second terminal.

11. The communication method according to claim 10 , wherein the indicated case for the first terminal is switched among the plurality of cases in accordance with a number of terminals connected to the base station, the terminals including at least the first and second terminals.

12. A communication method performed by a first terminal, the communication method comprising: receiving, from a base station, higher-layer signaling containing configuration information indicating a plurality of cases each indicating a first combination of control channel regions to be monitored by the first terminal among a plurality of control channel regions and a second combination of control channel regions to be monitored by a second terminal among the plurality of control channel regions, and receiving, from the base station, dynamic signaling indicating one of the plurality of cases, the dynamic signal being in the form of a control signal in a DCI (downlink control information) format directed to the first and second terminals; and detecting control information directed to the first terminal in the control channel region corresponding to the one case indicated by the dynamic signaling among the plurality of cases, wherein the first combination indicated by the one case to be monitored by the first terminal is different from the second combination indicated by the one case to be monitored by the second terminal.

13. The communication method according to claim 12 , wherein the indicated case for the first terminal is switched among the plurality of cases in accordance with a number of terminals connected to the base station, the terminals including at least the first and second terminals.